Load compensating arrangement for a vehicle suspension



3,079,171 LOAD COMPENSATING ARRANGEMENT FOR A VEHICLE SUSPENSIONOriginal Filed Dec. 3, 1959 Feb. 26, 1963 R. s. DICKINSON 2 Sheets-Sheet1 m w 7 9.. S. T 2 G 5 3 M m M/A 5 M 8 N m FIG] 3,079,171 LOADCOMPENSATING ARRANGEMENT FOR A VEHICLE SUSPENSION Original Filed Deca,1959 Feb. 26, 1963 R. s. DICKINSON 2 Sheets-Sheet 2 INVENTOR.

RONALD s. DICKINSON BY W M, 7 W

A TTORNEY' United States Patent finite 3,079,171 Patented Feb. 26, 19633,079,171 LOAD COMPENSATHNG ARRANGEMENT FOR A VEHIQLE SUSPENSEON RonaldSidney Dickinson, Osbaldwick, York, England, assignor to ArmstrongPatents Co. Limited, Beverley, Yorkshire, England, a British companyOriginal application Dec. 3, 1959, Ser. No. 857,114, new Patent No.3,021,153, dated Feb. 13, 1962. Divided and this application Sept. 22,1961, Ser. No. 157,299 Claims. (Cl. 280-124) This application is adivision of my co-pending application Serial No. 857,114, filed December3, 1959, now Patent No. 3,021,153, said co-pending application being acontinuation-in-part of my now abandoned application, Serial No.738,464, filed May 28, 1958.

The present invention concerns road vehicle suspension systems.

In most types of vehicle suspensions, especially those utilising metalsuspension springs, the distance between the Wheel mounting and thechassis or frame is variable, being dependent upon the load carried bythe chassis or frame and the resilience of the springs supporting thechassis or frame from the wheel mountings.

An object of the present invention is to provide an arrangement formaintaining a substantially uniform distance between the wheel mountingand the chassis or frame of a motor vehicle, irrespective of the loadingconditions on the vehicle chassis or frame.

Another object of the invention is to provide a load compensatingarrangement for a vehicle suspension in which hydraulic pump meansoperable responsive to normal road surface irregularities are employedin co-operation with hydraulic relief means to maintain the displacementbetween a vehicle wheel mounting and the vehicle frame within apredetermined range of displacements.

Yet another object of the invention is to provide hydraulic ram meanshaving a cylinder member with a movable member therein adapted to modifythe attitude of a suspension spring relative to the vehicle frameresponsive to changes in vehicle loading.

These and other objects of the invention will be described further, byway of example, with reference to the accompanying drawings, in which:

FIG. 1 is a sectional elevation of a shock absorber and control unitused in the present invention;

FIG. 2 is a sectional elevation on the line II-II of FIG. 1; and

FIGS. 3 to 6 are generally diagrammatic end elevations of embodiments ofthe invention employing pneumatic springs.

Throughout the drawings, similar reference numerals are employedwherever appropriate to denote similar parts.

In the embodiment illustrated in FIGS. 1, 2 and 5 there is shown acontrol unit 24 (1 18 in FIG. 5) which comprises a pair of substantiallyparallel cylinders 2 and 3 which communicate with one another by way ofports 7 and 7a at their lower ends, and through valve chamber 8 whereinare arranged valves 8a and 8b adapted to provide differential pressurepaths to hydraulic medium between the two cylinders, on compression andrebound movements of the wheel through lever 112 (FIG. 5). In FIGS. 1and 2 the cylinder 3 is shown as co-operating with its piston 5 toconstitute a pump for supplying conduit 25 with a hydraulic medium whichis placed under pressure by the pump against the reaction of the shockadsorber valves 8a and 8b. The cylinder 3 communicates via port 7, valvechamber 8 and passage 9 with the conduit 25. A means sensitive to theriding height of the vehicle is constituted by a relief valve 26communicating with conduit 25 by way of passage 26a, the valve 26 beingplaced in open or closed condition by means of a depressed cam surface 6formed on the yoke 22 and arranged to act on the stem 26b of the valve26. It will be appreciated that the cam surface 6 may 'be formedseparately from the yoke 22 if desired. The valve stem 26b is providedwith longitudinal grooves to enable hydraulic medium flowing through thepassage 26a to pass to a reservoir chamber 27 and/ or an auxiliaryreservoir provided in or independently of the combined shock absorberand control arrangement 24 above the cylinders 2 and 3 thereof. The camsurface 6 is so arranged on the yoke 22 as to be just incident upon thevalve stem 26b when the piston 5 is at a desired mean position in thecylinder 3, and the vehicle is at a desired riding height.

In the operation of the embodiment of the invention illustrated in FIGS.1, 2, and 5, assuming firstly that the vehicle is at its desired ridingheight, and that the cam surface 6 is incident upon the valve stem 26bof the relief valve 26, riding movements of the wheel arising fromcontinued travel of the vehicle will be transmitted by the lever arm 112to the rocking shaft 116 and hence to the yoke 22. The pistons 4 and 5will hence oscillate in their cylinders 2 and 3 in conventional mannerto co-operate with the valves 8a, 8b in imparting shock absorbing actionto the axle 11, and this motion of the piston 5 in its cylinder 3 willcause hydraulic medium to be transferred through the conduit 25 ('FIG.3) or conduit (FIG. 5) to the ram cylinder 154. The ram 152 is thusslightly displaced from the cylinder .154, and slightly raises thechassis member 114. Immediately this happens, however, the shaft 23 isangularly displaced by the consequent depression of the lever .112, andthe yoke 22 is angularly displaced to depress the valve stem 26b andlift the valve 26 momentarily off its seat. Thus, the ram cylinder 154is placed, by way of conduit 25 (FIG. 3) or conduit 160 (FIG. 5),passage 26a and valve 26 in communication with the reservoir 27 and asmall quantity of hydraulic medium is allowed by the momentary openingof valve 26 to exhaust from the ram cylinder into the reservoir, untilthe ram 152 has restored the wheel and chassis member 114 to theirdesired mean spacing. As long as the load on the vehicle remainsunchanged, therefore, the operation of the suspension remains asdescribed above, with momentary opening and closing of the valve 26taking place to maintain the vehicle at a mean riding height despite theconstant pumping action of the piston 5.

Should the load on the vehicle be increased, however, so that thechassis member 15 sinks and lifts the lever 112, then the yoke 22 ismoved anticlockwise by the shaft 23, and the cam surface 6 comes intoregister with the valve stem 26b, causing the valve 26 completely toclose. Continued riding movements of the vehicle then cause the piston5, in oscillating due to those movements, to pump hydraulic medium fromthe cylinder 3 to the ram cylinder 154, whereby the ram 152 is displacedfrom the cylinder to restore the spacing between the chassis member 15and wheel to its mean value, thus restoring the vehicle riding height toits desired mean value. Displacement of the ram 152 from the cylinder154 continues, of course, until consequent clockwise movement of theyoke 22 resulting from the restoring effect of the ram 152 moves the camsurface 6 off the valve stem 26b and allows valve 26 to resume therepeated momentary opening and closing procedure described above.

Conversely, should the load on the vehicle be decreased, then the yoke22 is moved clockwise as the spacing between the chassis member 114 andthe wheel increases, and consequently hydraulic medium is allowed toexhaust from the ram cylinder 154 back into the reservoir 27 until theram 152 has re-entered the cylinder 154 to an extent sutficient torestore the chassis 114 and wheel spacing to its required mean value.

The application of the invention to pneumatic spring suspensions isshown in FIGS. 3 to 6 of the drawings.

Referring now to FIG. 3 there is shown a vehicle suspension wherein thepneumatic springs 136 are of bellows construction, each comprising aplurality of interconnecting and superposed toroidal chambers closed byimperforate end plates. Each pneumatic spring is secured at one end toone of the lower levers 119 and at each upper end carries a hydraulicram 138 which is in turn secured to the vehicle chassis or frame 114 Le.is interposed between the vehicle chassis or frame and the pneumaticspring. Each hydraulic ram is connected by the conduit 14% to one of theshock absorbers v118. In the operation of this embodi-ment of theinvention the pumping action exerted by the shock absorbers 118, coupledwith the repeated momentary opening of the relief valves incorporatedtherein, serves to maintain the chassis or frame 114 at the desiredriding height so long as the vehicle loading remain un- A changed. Ifthe vehicle loading is increased however the relief valves are closeddue to the rotary displacement of the shafts 116 by levers 112 and theshock absorbers 118 supply hydraulic medium under pressure to thehydraulic rams 138 to cause the same to extend and raise the chassis 114relative to the wheel mounting. Expansion of the ram 138 ceases when theshafts 116 once again commence to effect repeated momentary openings ofthe relief valves. If the vehicle loading is decreased, of course, therelief valves open to allow hydraulic medium to exhaust from theramsback to the shock absorber reservoirs.

FIG. 4 shows an embodiment of the invention wherein a hydraulic ramcylinder 142 housing a displaceable ram 144 is secured to each of thelower levers 11%. To the vehicle chassis -or frame 114 are secured apair of pneumatic pressure chambers 146, the lower faces of which areclosed by flexible or elastic diaphragms 148- to which the outer ends ofthe rams 144 are fixedly connected. The hydraulic cylinders 142 areconnected by way of conduits .150 with the shock absorbers 118.Theoperation of this embodiment of the invention is similar to that ofthe embodiment already described above, in that increased vehicleloading causes the hydraulic shock absorbers 118 to pump hydraulicmedium under pressure in the cylinders 142 and so to cause extension ofthe rams 144 serving to raise the vehicle chassis or frame 114 until:such time as the resulting rotary displacement of shafts 116 (shaft 23of FIGS. 2 and 3) once again permits momentry operation of the reliefvalves. If the vehicle loading is decre'ased,the relief valves simplyopen to allow hydraulic medium to exhaust from the cylinders 142 back tothe reservoirs of the shock absorbers 118.

A somewhat similar embodiment of the invention to 'th-at'of FIG. 4 isshown in FIG. 5, with the difference that in FIG. the hydraulic mediumafiecting extension of retnaction of the ram is interposed between theram and the pneumatic sprin". It will be seen in FIG. 5 that the lowerlever 110 has a ram 152 pivotally attached thereto and displaceable in acylinder .154 which at its upper end is closed by a flexible diaphragm156. The flexible diaphragm 156 is retained on the cylinder 154 by meansof an annular end cap 158 which is in turn secured to the vehiclechassis or frame 114. The space enclosed by the flexible diaphragm 156is filled with hydraulic medium supplied from the shockabsorbers 118 byway of conduit 160 and the space between the flexible diaphragm 156 andthe annular end cap 158 constitutes a pneumatic suspension spring. Themovement of the hydraulic medium between the shock absorber 118 andcylinder 154, controlled by the relief valve an described above, resultsin extension or retraction of the ram 152 within cylinder 154 tocompensate for increased or decreased vehicle 7 loading.

being mounted between the lower lever 11% and the vehicle chassis orframe 114. To the lower end of the spring 162 is connected a hydraulicconduit 164 adapted to supply hydraulic medium under pressure from theshock absorber 113 to the interior of spring 162, thereby to act againsta pneumatic medium filling the remainder of the interior of spring 162.The addition of hydraulic medium to spring 1&2. or the exhaust ofhydraulic medium therefrom will be observed to result in extension orcontraction of spring 1621 to compensa e respectively for increases ordecreases in vehicle loading in much the same way as already described.

This application is a continuation-in-part of my copending applicationSerial No. 738,464 filed May 28, i958, now abandoned.

I claim:

In a vehicle suspension system comprising a vehicle wheel mounting, avehicle frame, said wheel mounting having an upper and a lower linkmember pivotally connected to said frame, a pneumatic suspension springsupporting said frame upon said wheel mounting, said pneumaticsuspension spring being seated in compression between the frame and oneof said link members, and a double acting hydraulic shock absorbercoupled between said frame and said wheel mounting to damp vibrations ofsaid suspension spring, said shock absorber having a compression chamberand rebound chamber containing hydraulic medium connected to each otherby a valve controlled passage, and a piston assembly positioned withinsaid chambers in accordance with the displacement between said frame andsaid wheel mounting and operable to displace fluid from one of saidchambers to the other through said valve controlled passage inaccordance with relative movement between said wheel member and saidframe; the improvement comprising means defining a hydraulic reservoir,a hydraulic ram means having a cylinder member and a movable membertherein, said hydraulic ram means being positioned to act directly onsaid pneumatic spring for varying the displacement between said wheelmounting and said frame in accordance with the pressure of hydraulicmedium in said cylinder member, a first conduit connecting said cylindermember to said reservoir for transferring hydraulic medium between saidcylinder member and said reservoir, a first one way valve in saidconduit adjacent said reservoir normally seated to prevent flow ofhydraulic medium into said reservoir, a second conduit connecting saidvalve controlled passage to said first conduit at a location betweensaid first one way valve and said cylinder member, a sec- 0nd one wayvalve in said second conduit permitting flow of hydraulic mediumtherethrough only from said valve controlled passage into said firstconduit when the pressure in said passage exceeds the pressure in saidfirst conduit, and cam means coupled to said piston assembly for openingsaid first one way valve when the displacement between said wheelmounting and said frame differs from a predetermined range ofdisplacements.

2. A vehicle suspension as defined in claim 1 wherein one of saidhydraulic ram members is carried by said frame.

3. A vehicle suspension as defined in claim 1 wherein one of saidhydraulic ram members is carried by said one link member.

4. A vehicle suspension as defined in claim 1 wherein a pneumatic springcomprises a chamber secured to said frame, and a flexible diaphragmclosing the region of said chamber remote from said frame, one member ofsaid hydraulic ram means being connected to said flexible diaphragm andthe other member of said ram means being carried by one of said linkmembers.

5. A vehicle suspension as defined in claim 1 comprising an end cap forsaid cylinder member of said hydraulic ram means, said end cap beingcarried by said vehicle frame, a flexible diaphragm clamped between saidcylinder member and said-end cap and cooperatingwith-the latter todefine a pneumatic chamber constituting said pneumatic spring means,said movable member of said ram means being a piston member engaged insaid cylinder member, said piston member being connected to one of saidlink members, and means for admitting said hydraulic medium to saidcylinder member between said piston member and said diaphragm.

References Cited in the file of this patent UNITED STATES PATENTS RabeJune 6, 1939 Cross June 29, 1943 Heiss Mar. 4, 1958 Heiss Mar. 24, 1959Moustakis July 28, 1959 Walker Nov. 10, 1959

1. IN A VEHICLE SUSPENSION SYSTEM COMPRISING A VEHICLE WHEEL MOUNTING, AVEHICLE FRAME, SAID WHEEL MOUNTING HAVING AN UPPER AND A LOWER LINKMEMBER PIVOTALLY CONNECTED TO SAID FRAME, A PNEUMATIC SUSPENSION SPRINGSUPPORTING SAID FRAME UPON SAID WHEEL MOUNTING, SAID PNEUMATICSUSPENSION SPRING BEING SEATED IN COMPRESSION BETWEEN THE FRAME AND ONEOF SAID LINK MEMBERS, AND A DOUBLE ACTING HYDRAULIC SHOCK ABSORBERCOUPLED BETWEEN SAID FRAME AND SAID WHEEL MOUNTING TO DAMP VIBRATIONS OFSAID SUSPENSION SPRING, SAID SHOCK ABSORBER HAVING A COMPRESSION CHAMBERAND REBOUND CHAMBER CONTAINING HYDRAULIC MEDIUM CONNECTED TO EACH OTHERBY A VALVE CONTROLLED PASSAGE, AND A PISTON ASSEMBLY POSITIONED WITHINSAID CHAMBERS IN ACCORDANCE WITH THE DISPLACEMENT BETWEEN SAID FRAME ANDSAID WHEEL MOUNTING AND OPERABLE TO DISPLACE FLUID FROM ONE OF SAIDCHAMBERS TO THE OTHER THROUGH SAID VALVE CONTROLLED PASSAGE INACCORDANCE WITH RELATIVE MOVEMENT BETWEEN SAID WHEEL MEMBER AND SAIDFRAME; THE IMPROVEMENT COMPRISING MEANS DEFINING A HYDRAULIC RESERVOIR,A HYDRAULIC RAM MEANS HAVING A CYLINDER MEMBER AND A MOVABLE MEMBERTHEREIN, SAID HYDRAULIC RAM MEANS BEING POSITIONED TO ACT DIRECTLY ONSAID PNEUMATIC SPRING FOR VARYING THE DISPLACEMENT BETWEEN SAID WHEELMOUNTING AND SAID FRAME IN ACCORDANCE WITH THE PRESSURE OF HYDRAULICMEDIUM IN SAID CYLINDER MEMBER, A FIRST CONDUIT CONNECTING SAID CYLINDERMEMBER TO SAID RESERVOIR FOR TRANSFERRING HYDRAULIC MEDIUM BETWEEN SAIDCYLINDER MEMBER AND SAID RESERVOIR, A FIRST ONE WAY VALVE IN SAIDCONDUIT ADJACENT SAID RESERVOIR NORMALLY SEATED TO PREVENT FLOW OFHYDRAULIC MEDIUM INTO SAID RESERVOIR, A SECOND CONDUIT CONNECTING SAIDVALVE CONTROLLED PASSAGE TO SAID FIRST CONDUIT AT A LOCATION BETWEENSAID FIRST ONE WAY VALVE AND SAID CYLINDER MEMBER, A SECOND ONE WAYVALVE IN SAID SECOND CONDUIT PERMITTING FLOW OF HYDRAULIC MEDIUMTHERETHROUGH ONLY FROM SAID VALVE CONTROLLED PASSAGE INTO SAID FIRSTCONDUIT WHEN THE PRESSURE IN SAID PASSAGE EXCEEDS THE PRESSURE IN SAIDFIRST CONDUIT, AND CAM MEANS COUPLED TO SAID PISTON ASSEMBLY FOR OPENINGSAID FIRST ONE WAY VALVE WHEN THE DISPLACEMENT BETWEEN SAID WHEELMOUNTING AND SAID FRAME DIFFERS FROM A PREDETERMINED RANGE OFDISPLACEMENTS.